Investigations into improved electrochemical performance of Sn doped Hard carbons as negatives for Na-ion batteries

Abstract

Hard carbon is the most suitable anode material for pragmatic Sodium-ion batteries (NIBs). Despite various studies, there is still significant scope for improvement in the understanding of the (de)sodiation mechanism. Here, we study Sn incorporation in hard carbons and its effects on the electrochemical performance. Sn incorporation leads to improved first cycle coulombic efficiency and capacity, specifically increase in the plateau capacity. An improvement from 220 mAh/g to 285 mAh/g and 325 mAh/g is respectively obtained for 7% and 15% Sn in hard carbon-Sn composites (HC/Sn). Sn incorporation in both commercial and sucrose-derived hard carbons has been shown to improve the electrochemical performance. X-ray diffraction (XRD) studies show that number of graphene layers in nano-graphitic domains is reduced after Sn incorporation with no change in interlayer spacing, thus highlighting the role of the nature of graphitic domains in designing the hard carbons. Full cells with commercial cathodes are also presented. Cost analysis of the Sn doping routes in this study is presented to demonstrate the commercial viability of the strategy.